Green Chemistry in Mineral Processing

(De Gruyter) – The leaching of valuable metals from mineral ores is the basis of several extractive economies around the world, but the strategies employed often need to rely on dangerous compounds such as cyanides. However, “greener” agents are significantly less favorable than cyanide for complexing noble metal ionsEven though mining companies have a robust set of strategies for the handling and disposal of cyanide, the high toxicity of this compound is an environmental and social concern. Due to the complex nature of most ores, leaching processes are slow and have a low efficiency in noble metal extraction, which is usually improved by fine-milling the mineral.

The authors consider an alternative strategy, demonstrating that it may increase the amount of silver leaching, but at the expense of a higher consumption of cyanide, which renders the process inefficient (only 2% of consumed cyanide is employed to complex silver). The increase in the yield of the desired product without the smarter use of dangerous compounds is shown as a paradigm of the need to insert green chemistry principles in industrial processes.

Results of two potential strategies for greener mineral processing are shown: the use of ultrasound to eliminate passivating layers formed during the leaching process and the use of chemical pretreatments to eliminate possible sources of passivation. These strategies can increase the amount of silver extraction and simultaneously increase the efficiency in cyanide consumption. The convenience of these pretreatments in the framework of the green chemistry principles, as well as the challenges towards their implementation at industrial scale, is discussed.

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Edited for Content and Length by Dr. Matthew A. Hood.

The  full article can be found at De Gruyter in the Scientific Journal of IUPAC, Pure and Applied Chemistry.            2017 IMPACT FACOR 5.294

DOI: 10.1515/pac-2017-0904

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